<template>
  <div class="spec-preview" @mousemove="handelEvent">
    <img :src="image.imgUrl" />
    <div class="event" ref="event"></div>
    <!-- 右侧大盒子 -->
    <div class="big" >
      <img :src="image.imgUrl" :style="`top:${-top*2}px;left:${-left*2}px`"/>
    </div>
    <!-- 遮罩层 -->
    <div class="mask" :style="`top:${top}px;left:${left}px`" ></div>
  </div>
</template>

<script>
import throttle from "lodash/throttle"
import {offset} from "@/utils"
  export default {
    name: "Zoom",
    data(){
      return {
        top:0,
        left:0,
        offset:{}
      }
    },
    props:{
      image:{
        type:Object,
        default:()=> ({}) //默认是一个空对象
      }
    },
    mounted(){
      this.offset = offset(this.$refs.event)
    },
    methods:{
      //节流函数
      handelEvent:throttle(function(e){
         
        let left= e.pageX - this.offset.left - 100
        let top= e.pageY - this.offset.top -100
       
        //数据写死，性能更好
        // let left= e.offsetX - 100
        // let top= e.offsetY - 100

        if(top < 0) top = 0
        if(top > 200) top=200

        if(left <0) left = 0
        if(left > 200) left=200
      //  console.log(top,left);
        this.left =left
        this.top =top

       
      },50)
      
    }
  }
</script>

<style lang="less">
 .spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 2;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.315);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 2;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>